[ZT] Add cert to Docker (#17783)

Author: maxvp

src/content/docs/cloudflare-one/connections/connect-devices/warp/user-side-certificates/manual-deployment.mdx

@@ -489,6 +489,143 @@ On some systems you may need to set the following in your path/export list:
 export NODE_EXTRA_CA_CERTS='[PATH_TO_CLOUDFLARE_CERT.pem]'
 ```
 
+### Docker
+
+To install a certificate for use in a Docker container:
+
+1. [Download a Cloudflare certificate](#download-the-cloudflare-root-certificate) in `.pem` format.
+2. Create a directory for certificates in your Docker project:
+
+   ```sh
+   cd docker-project
+   mkdir certs
+   mv /path/to/downloaded/certificate.pem certs/
+   ```
+
+3. Verify the certificate was moved to the directory correctly. Your project should have the following structure:
+
+   ```sh
+   docker-project/
+   ├── Dockerfile
+   └── certs/
+       └── certificate.pem
+   ```
+
+4. Add the certificate to your Docker image:
+
+   <Tabs> <TabItem label="During build process">
+
+   To add the certificate to your Dockerfile to install it during the build process:
+
+   1. Add the certificate install directions to your Dockerfile. For example:
+
+      ```docker title="Red Hat-based images"
+      FROM registry.access.redhat.com/ubi9/ubi:latest
+      # Or FROM centos:7 or FROM fedora:38
+
+      # Install necessary certificates package
+      RUN dnf install -y ca-certificates
+
+      # Copy and add Cloudflare root certificate
+      COPY certs/certificate.pem /etc/pki/ca-trust/source/anchors/certificate.crt
+      RUN update-ca-trust extract
+      ```
+
+      ```docker title="Debian-based images"
+      FROM debian:12
+      # Or FROM ubuntu:22.04
+
+      # Install necessary certificates package
+      RUN apt-get update && apt-get install -y ca-certificates
+
+      # Copy and add Cloudflare root certificate
+      COPY certs/certificate.pem /usr/local/share/ca-certificates/certificate.crt
+      RUN update-ca-certificates
+      ```
+
+      ```docker title="Alpine-based images"
+      FROM alpine:3.18
+
+      # Install necessary certificates package
+      RUN apk add --no-cache ca-certificates
+
+      # Copy and add Cloudflare root certificate
+      COPY certs/certificate.pem /usr/local/share/ca-certificates/certificate.crt
+      RUN update-ca-certificates
+      ```
+
+   2. Build the Docker image:
+
+      ```sh
+      docker build -t <your-container-name> .
+      ```
+
+   3. Verify the certificate was installed:
+
+      ```sh title="Red Hat-based images"
+      docker run --rm your-image-name sh -c "cat /etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem | grep Cloudflare"
+      ```
+
+      ```sh title="Debian and Alpine-based images"
+      docker run --rm your-image-name sh -c "cat /etc/ssl/certs/certificate.pem"
+      ```
+
+   </TabItem>
+
+   <TabItem label="During runtime">
+
+   To add the certificate to your Docker Compose file to install it during runtime:
+
+   1. Add the certificate install directions to your `docker-compose.yml` file. For example:
+
+      ```yaml title="Red Hat-based containers"
+      version: '3'
+      services:
+      	redhat-app:
+      		image: registry.access.redhat.com/ubi9/ubi:latest
+       		volumes:
+       			- certs/certificate.pem:/etc/pki/ca-trust/source/anchors/certificate.pem
+       		entrypoint: /bin/sh -c "dnf install -y ca-certificates && update-ca-trust extract && app start"
+      ```
+
+      ```yaml title="Debian-based containers"
+      version: '3'
+      services:
+      	debian-app:
+      		image: debian:12
+       		volumes:
+       			- certs/certificate.pem:/usr/local/share/ca-certificates/certificate.crt
+       		entrypoint: /bin/sh -c "apt-get update && apt-get install -y ca-certificates && update-ca-certificates && app start"
+      ```
+
+      ```yaml title="Alpine-based containers"
+      version: '3'
+      services:
+      	alpine-app:
+      		image: alpine:3.18
+       		volumes:
+       			- certs/certificate.pem:/usr/local/share/ca-certificates/certificate.pem
+       		entrypoint: /bin/sh -c "apk add --no-cache ca-certificates && update-ca-certificates && app start"
+      ```
+
+   2. Run the container:
+
+      ```sh
+      docker-compose up
+      ```
+
+   3. Verify the certificate was installed:
+
+      ```sh title="Red Hat-based containers"
+      docker exec -it <container-name> sh -c "cat /etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem | grep Cloudflare"
+      ```
+
+      ```sh title="Debian and Alpine-based containers"
+      docker exec -it <container-name> sh -c "cat /etc/ssl/certs/ca-certificates.crt | grep Cloudflare"
+      ```
+
+   </TabItem> </Tabs>
+
 ### Google Cloud
 
 #### Google Cloud SDK